Patent GB-655848-A (GB)
Title: Apparatus for maintaining a predetermined but adjustable relationship between two variables in a physical process or for giving an indication dependent on two variables in a physical process
IPC: G05D11/03
Filed: 1948-03-19
Abstract: 655,848. Indicating-apparatus. FOXBORO CO. March 19, 1948, No. 8264. Convention date, April 24, 1947. [Class 106 (iv)] [Also in Group XXIX] Apparatus for maintaining a predetermined but adjustable relationship between two variables or for giving an indication dependent on two variables comprises two pivoted elements arranged to lie in a straight line when in neutral position with pivots adjacent and two links pivoted to the elements and to one another at a movable pivot on one side of the line and a third link pivoted about an adjustable point on the other side of the line and also to the first two links at their common pivot, the parts being so arranged and proportioned that the extent of movement of one element is proportional to that of the other in a ratio determined by the position of the adjustable point and each of two of the three entities consisting of the two elements and the said point being responsive to or controlling an associated one of the two variables. The invention is shown diagrammatically in Fig. 4 which illustrates means for transmitting motion from an element 10 pivoted at 12 to an element 14 pivoted at 16 in a ratio predetermined by the setting of an element 34 pivoted at 32, comprising three links 26, 28, 40 pivoted together at 30 and pivoted respectively to the three elements 10, 14, 34. An embodiment of the invention comprising apparatus for maintaining a predetermined but adjustable relationship between an independent flow of fluid and a dependent flow comprises two elements 46, 48 responsive to the two elements 46, 48 responsive to the two flows, Fig. 5, so as to move levers 50, 52 proportionally thereto and a control device which may be of a pneumatic type and may include a baffle 92 urged toward a nozzle 94 by a spring 96 and which may be moved away by rotation of a lever 98 through a post 100 on a lever 102, the the baffle and nozzle co-operating to position a valve to regulate the dependent flow. A change in the independent flow causes the lever 50 to move a link 53 to rotate a bell-crank lever 68 whose arcuate arm frictionally engages a shaft 70 to turn a bracket 62 whose rear arm moves a link 184 while its upper arm controls means for recording the flow. A linkage assembly 58 converts movement of the link 184 into a proportional movement of a link 186 in a ratio set on a disc 138 against an index 136 by means analogous to those shown in Fig. 4 and the link 186 sets angularly a bracket 66 having two rear arms between which is pivoted a bell-crank 86. One arm of the bell-crank 86 is held by a link 88 attached to a sector 74 so that movement of its pivot point with the bracket 66 causes its other arm to actuate the control device through a link 90. The change in the dependent flow affects the element 48 to move the lever 52 and a link 54 and so turn a bell-crank 76 whose arcuate arm frictionally engages a shaft 78 to turn a bracket 64 fixed to the sector 74 which through the link 88 turns the bell-crank 86 about its pivot to move the link 90 and actuate the control device, while the upper arm of the bracket 64 controls means for recording the dependent flow. The linkage assembly 58 comprises an arm 164b, free on a shaft 162 and pivoted to the link 184, which transmits motion to a lever 178, pivoted to the link 186 and mounted on a shaft 176 pivoted in plates 112, 114, in a ratio predetermined by the setting of a sector 118, pivoted to a bush in a base 106 with a spring washer inserted between the head of a screw and the bush, by means of three links 154, 156 and 150 pivoted together on a pin, the link 150 being pivoted to the sector 118 and the links 154, 156 being urged toward one another by a spring 158. The arm 164b is urged by a spring 166 into contact with an upturned end 170 of a lever 168, which lever 168 therefore follows the arm's movements and, being connected by an adjusting screw 172 to a lever 160 fixed to the spindle 162 and pivoted to the link 154, transmits the movements through the link 156 and a lever to which the link 156 is pivoted and which is connected by an adjusting screw 180 to a lever fixed to the spindle 176 to the lever 178 and link 186. The sector 118 may be positioned manually or automatically. Other embodiments of the invention may be applied to correcting for pressure or temperature when measuring the flow of a fluid, to indicating the ratio between two flows or to adjusting the proportioning band of an automatic controller.